MLA

Mitchell, Donald Grant, 1822-1908. Stowe, Harriet Beecher. Box 6. 1868-1870. https://collections.library.yale.edu/catalog/32307970.

APA, 6th edition

Mitchell, Donald Grant, 1822-1908. (["Box 6"])(1868-1870)[Stowe, Harriet Beecher]. https://collections.library.yale.edu/catalog/32307970.